Hope this isn't a repeat question. Fairly new to AG brewing. I looked all night for an answer to my question below, but I didn't find any satisfying answer.

I have a Megapot, that I am using as my mash tun. Two gallons of water sit below the false bottom. I am doing my second batch tomorrow which calls for 2.8 gallons of mash water. With my MT that won't cover the grain. So to adjust I am planning on using about 5 gallons total (2 below FB and 3 above FB) to do my mash. With that said I have to adjust my sparge water correct? I use the mash/sparge water calculator from brew365.com. I calls for 8.5 gallons of total water needed. But it wants me to do 2.8 gal Mash and 5.7 gal Sparge. But my equipment won't allow for that. Will it affect the beer to do a bigger volume of mash water and smaller amount of sparge? My mash water volume will be 5 gallons, leaving only 3.5 gallons for the sparge. I that going to screw up efficiency, taste, or anything else?

Do you have a pickup tube so you can siphon that water from below the FB?

I set up a screen over the output inside the pot. Just going to tilt the MT so I can get the rest out. Not too concerned about that so much as that 2 gallons sitting below the grain, having little to no interaction with the grain and that affecting the efficiency.

I've got the same situation. I basically ignore the water below and mash a bit on the thin side 1.25-1.5 qts/lb. That said I usually mash 12+ lbs, so the effective mash ratio is higher. I mean that with a smaller grain bill, that two gallons decreases the ratio more.

As for efficiency, I don't know, but if you get full conversion with an iodine test, then you've got full conversion. You may lose efficiency with having less sparge water. I fly sparge and have good enough efficiency.

I've got the same situation. I basically ignore the water below and mash a bit on the thin side 1.25-1.5 qts/lb. That said I usually mash 12+ lbs, so the effective mash ratio is higher. I mean that with a smaller grain bill, that two gallons decreases the ratio more.

As for efficiency, I don't know, but if you get full conversion with an iodine test, then you've got full conversion. You may lose efficiency with having less sparge water. I fly sparge and have good enough efficiency.

I have only done one other AG brew with this set up and my calculated efficiency was 82%. Dumb luck I guess. That was a 13 lb grain bill though. My next is 8.5 lbs, so I will probably lose some efficiency then. Guess I won't worry about it too much until it becomes an issue.

Or, you can get a 1/2" SS elbow and 1/2" barb to use as a pickup tube under the false bottom you have that will only leave about .25 gallons left as well with a proper siphon.

Or you can keep doing what you are doing but you will have to bump up your grain calculations to account for leaving 2 gallons of wort behind. However, for smaller beers, this setup is sometimes a problem because of that 2 gallons below the false bottom. I ultimately switched to the NB false bottom because of this issue.